Tuesday 10 November 2009 11.57 EST
First published on Tuesday 10 November 2009 11.57 EST

China's most populous river needs massive investment and careful planning to ease the impact of climate change, which is causing floods, droughts and storms to intensify, a new report (pdf) said today.

The Yangtze delta, which is home to about 400 million people, has been warming far faster than the global average for more than a decade and the implications for food security and biodiversity will worsen without remedial action, according to the study led by WWF China.

The report found that in the first five years of this decade, temperatures along China's biggest river have increased by 0.71C, after a rise of a third of a degree in the 1990s.

The consequences are already apparent, from the source to the estuary. The report's authors – which includes many of China's leading scientists – calculated that climate change was responsible for 81% of grassland degradation near the headwaters of the Yangtze on the Tibetan plateau. By the estuary near Shanghai, the sea level had risen by 11.5cm in the past 30 years.

As well as having a dire impact on wildlife, particularly in wetlands, the report warned that people living on the delta would have to adapt or suffer from falling harvests, lengthening droughts and fiercer storms.

If current trends continue, it predicted rice production in the Yantgtze basin would decrease by between 9% and 41% by the end of the 21st century, while harvest of corn and winter wheat would decline even more precipitously.

Large areas of southern China are already experiencing a crippling drought. Chinese climatologists say rainstorms are growing more frequent and intense, raising the risks of floods.

"Extreme climate events such as storms and drought disasters will increase as climate change continues to alter our planet," said Xu Ming, the lead researcher on the report, which included contributions from the China Academy of Sciences, the China Meteorological Administration and other academic bodies.

The study – one of the most comprehensive ever undertaken of a major river basin – was cautious about the rate of glacier shrinkage.

Despite the rising temperatures, it predicted the icefields near the headwaters would only shrink by 11.6% between 1970 and 2060. This is a slower rate of decline than previous studies.

The authors urged the authorities to ease the impact on people and the environment by developing hardier crop strains, shifting from corn to rice, improving the management of the river and dams, and by reinforcing dykes and power supply systems.

"Adaptation is a must for large developing nations such as China, which is particularly vulnerable to climate change because of its large population and relatively low economic development," said James Leape, director general of WWF International. "The report is a reminder that while the whole world rises to meet the challenge of climate change, we must prepare for impacts that are already inevitable," he said.